Improvement in case-hardening iron



one part with the intense and deep effect due GRAOIE ROBERTS, OF BROOKLYN, NEW YORK..

IMPROVEMENT IN CASE-HARDENING IRON.

Specification forming part of Letters Patent No. 204,846,

dated June 11, 1878 application filed March 6, 1876.

To all whom it may concern: Among the advantages of this invention Be it known that I, GRAOIE SAYRE ROB- are the following: First, that the materials, or ERTS, of the city of Brooklyn, county of Kings, the most expensive ones, being applied only State of New York, have invented certain new where needed, are economized secondly, that and useful Improvements relating to Case certain portions of the tool or other article of Hardening Iron, which are fully set forth in iron treated may by this process be case-hardthe following specification. ened or steeled, while all the rest may remain I case-harden any desired portion of the unchanged, by applying the coating only to iron at will, leaving the remainder unaffected those parts and using a packing material and I case-harden the same to various dewhich has no efiect upontheiron; thirdly, that grees or depths at different parts at the same different portions of the same tool or other tune. article of iron treated can be case-hardened As an example of what I esteem the best or steeled in different degrees at the same means of carrying out my invention, I take a time by changing the quantity or quality of by preventing ferrotool or other article of iron, certain portions thecoating; fourthly,that

cyanide of potassium or other chemicals from of which are required to be case-hardened or steeled, and after polishing the surface, as dissipation the action penetrates deeper than required, I glue to such portions a coating of when using them by simply sprinkling them yellow prussiate of otash'.- on the hot iron; fifthly, that this method is When the glue has set hard, 1 pack the more economical and easier, and more accuarticle in powdered charcoal, heat to redness rate of application, than the clay-protection process, and is more certain in its results,

in a quick fire, and maintain the heat for half an hour, or until the reactions or changes and can be applied at the wearing-points on have taken place to the required depth, and the inside of chain-links and the like, where then harden and temper in the usual manner. it would be almost, if not quite, impossible to The glue may be conveniently applied at use the other. the desired points with abrush, as in ordinary I claim as my improvement in case-hardengluing, and the prussiate may be dusted ing on till no more will adhere. After becoming 1. The process of producing case-hardened hard, a second coat of glue and of the chemarticles, which consists in coating the .whole ical may be applied on any part to increase or any desired portion with an adhesive mathe thickness there, and the degree or thickterial, next applying the case-hardening maness of the case-hardening will be accordterial as an exterior coating, and afterward in gly greater at the points thus thickly treated. subjecting the thus-prepared iron to heat in a I can use different material for the different packing of charcoal or analogous neutral or parts, instead of, or in addition to, the applinearly neutral material, as herein specified. cation of the coating in different thicknesses. 2. In case-hardening iron articles, the pro- Thus I can use yellow prussiate of potash on cess of applying the case-hardening material,

which consists in attaching it to any desired portion. of the article by means of glue, substantially as described.

3. In the production of case-hardened articles, the within-described method of casehardening-certain portions at will to diiferent depths by variably coating the different parts, as herein specified.

4. Iron articles having different portions case-hardened to different degrees, as herein specified.

GRAOIE SAYRE ROBERTS. Witnesses:

WM. WHITE WILsoN, RICHARD A. RoBERTs.

to the use of this chemical, and a cheaper chemical, or simply bone-black, on other parts where only a slight case-hardening effect is required.

I do not confine myself to the use of yellow prussiate of potash as the principal casehardening material, glue as the adhesive agent, nor charcoal as the packing material, as any competent chemist can easily suggest others to take their places. Cast, wrought, or malleable iron may be used.

The packing may or may not be of a character to aid directly in the case-hardening or steeling. 

